And finally tonight as you watch the big debate between the president and governor romney, see if you can spot the secret demands of the candidates. We have a copy of the rules negotiated for the showdown tonight. What they agreed they can and cannot do. And abc's jon karl has pored over the 21 pages. Reporter: Rock stars make all kinds of demands when they perform. VAN HALEN WANTS NO BROWN M&Ms IN The dressing room. Mariah carey insists on custom toilet paper, white roses and vanilla aromatherapy candles. Obama and romney have demands, too -- all in a 21-page agreement. Tonight, identical director's chairs and foot rests and they must stay in their predesignated area. No wandering around the stage LIKE john McCain or charging your opponent like al gore did to george bush. And like football, lots of koij tosses which determines who gets the first question. Past candidates had demands too. Al gore worried about sweating. Wanted the room 55 degrees and michael dukakis who is quite a bit shorter an the elder george bush negotiated a little boost hidden beneath the carpet behind the podium. Take a look at that again. As dukakis goes back behind the podium, he also gets up onto something the debate commission called the "pitcher's mound." And suddenly he's just about as tall as george bush. The obama/romney agreement says no height boost for ito candidate. One of these past candidates, we can't say which one, insisted that the cameras be repositioned so as not to show his bald spot. But never any demands about BROWN M&Ms. Jonathan karl, abc news, washington.

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